The present invention relates generally to the field of heating, ventilating and air conditioning (HVAC), and more specifically to the HVAC system for the operator's cabin of a locomotive, and particularly to a method and apparatus for reducing the noise generated by the HVAC system of a locomotive.
It is known to provide an HVAC system for controlling the environmental conditions inside the operator's cabin of a railroad locomotive. A typical system, as provided by the assignee of the present invention, includes a fan and heat exchanger assembly installed below the floor of the cabin, horizontal ducts running beneath the floor between the floor joists, a vertical duct running through the control compartment forming one wall of the cabin, and a plurality of outlets connected to both the horizontal ducts and the vertical duct. Because the space for ductwork is very limited in a locomotive, the velocity of air moving through the ductwork must be maintained at a generally high level in order to satisfy the heat load specifications established for such systems. As a result, there is a considerable amount of sound energy generated by the HVAC system in a locomotive cabin. In one application, the HVAC system of a locomotive operating at maximum fan speed generates a sound level of approximately 75 dbA in the locomotive cabin.